1. Field of the Invention
The present invention relates to an ultrasonic diagnostic apparatus, and more particularly, it relates to an ultrasonic diagnostic apparatus and an ultrasonic diagnostic apparatus control method capable of automatically setting a gain for a reception signal collected from a specimen.
2. Description of the Related Art
An ultrasonic diagnostic apparatus transmits and receives ultrasonic waves in a plurality of directions of a specimen using an ultrasonic probe in which a plurality of oscillating elements are arranged, and displays, on a monitor, image data generated on the basis of reflected waves obtained at the time. This apparatus enables a real-time observation of two-dimensional image data or three-dimensional image data on the inside of a body by a simple operation of touching the ultrasonic probe with the body surface, and is therefore widely used to diagnose the shapes or functions of various organs.
Such an ultrasonic diagnostic apparatus generally comprises an ultrasonic probe having oscillating elements for transmitting/receiving ultrasonic waves to/from a specimen, a sending unit for supplying a drive signal to the oscillating elements, a receiving unit for performing processing such as a gain correction for a reception signal obtained from the oscillating element, an image data generating unit for generating image data on the basis of the processed reception signal, and a display unit for displaying the generated image data.
The reception sensitivity in the transmission/reception of the ultrasonic waves carried out by the ultrasonic diagnostic apparatus having the above-mentioned basic configuration is dependent on the shape and tissue characterization of an organ which propagates the ultrasonic waves at this moment and further dependent on, for example, the degree of obesity of the specimen. Therefore, when the two-dimensional image data for the specimen is to be collected and displayed, an operator operates a gain correcting function provided in an input section under the observation of the image data displayed in real time on the display unit of the apparatus, thereby correcting the gain for the reception signal and generating image data having a preferred sensitivity distribution.
However, this method requires a new gain correction every change in the position or direction of a slice section (scan section) of the image data for a diagnostic part of the specimen, so that inspection efficiency significantly decreases, which has been a major problem particularly when ultrasound tests are conducted in a short time for a large number of specimens as in a screening test in, for example, a medical checkup.
In order to improve such a problem, there has been proposed a method of automatically correcting the gain of a reception signal on the basis of previously collected information on the amplitude of this reception signal (e.g., refer to Patent document 1 and Patent document 2.).
To automatically correct the gain of a reception signal, Patent Publication No. 2648771 describes a method comprising detecting a peak position of a histogram generated on the basis of information on the amplitude of this reception signal, and setting a gain correction value on the basis of the difference between the peak position of the histogram and a preset reference value corresponding to the average luminance of image data.
Furthermore, PCT National Publication No. 2004-500915 describes a method comprising determining a diagnostic living tissue region on the basis of the S/N of two-dimensional ultrasound data obtained from slice sections and a specimen or the dispersion value of a histogram, and setting a two-dimensional gain correction map for correcting a local gain or a dynamic range in the living tissue region on the basis of the amplitude information and noise level concerning the ultrasound data in the living tissue region.
Recently, attention has been focused on a method comprising transmitting/receiving ultrasonic waves to/from a three-dimensional region of a specimen, and generating three-dimensional image data or two-dimensional image data in an arbitrary section on the basis of volume data collected at the time. Methods of collecting the volume data in practical use include a method which moves or turns an ultrasonic probe having a plurality of one-dimensionally arranged oscillating elements in a direction perpendicular to the arrangement direction, and a method using an ultrasonic probe having a plurality of two-dimensionally arranged oscillating elements (two-dimensional array ultrasonic probe).
The above-mentioned volume data is usually generated by composing ultrasound data obtained in a plurality of sequential slice sections. Then, when such volume data is subjected to a gain correction in accordance with, for example, the method described in Patent document 1 or Patent document 2, it is necessary to set the above-mentioned gain correction values or gain correction maps for the two-dimensional ultrasound data obtained from a large number of slice sections and further set three-dimensional gain correction data on the basis of the obtained gain correction values or gain correction maps, which requires a storage circuit having a high capacity to store the ultrasound data for use in the gain correction and also requires much time spent on setting the three-dimensional gain correction data. It has therefore been difficult to display, in real time or in a short time, for example, three-dimensional image data based on the volume data which has subjected to the gain correction by the application of the above-mentioned methods.